Deep HOMO polymers comprising anthracene units for bulk heterojunction solar cells

• The polymers include BO has a lower lying oxidation potential than BT, it typically increases the value of Voc.
• The structure–property relationships caused by the side chains of anthracene were investigated.
• PAnoBO and PAnoBO-EH exhibited increase Voc, Jsc and power conversion efficiency (PCE) compared with PAnoBT-EH.

Four anthracene-based D–π–A polymers, poly[anthracene-alt-4,7-bis(thiophen-2-yl)-5,6-bis(octyloxy)benzo[c][1,2,5]thiadiazole] (P1, P3) and Poly[anthracene-alt-4,7-bis(thiophen-2-yl)-5,6-bis(octyloxy)benzo[c][1,2,5]oxadiazole] (P2, P4), were successfully polymerized through Suzuki coupling reaction. The polymers include benzooxaediazole (BO), PAnoBO, and PAnoBO-EH exhibited the deep HOMO level (−5.39 eV or lower) because BO has a lower lying oxidation potential than Benzothiadiazole (BT). BO acceptor enhanced the electron withdrawing property of the polymers, inducing long-wavelength absorption and 0.05–0.1 eV reduction in the band-gap. For solar cells using a PAnoBO:PC71BM (1:4, w/w), the resulting Jsc, Voc, FF, and PCE were 3.1 mA/cm2, 0.74 V, 48.8%, and 1.2%, respectively.

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